This contribution proposes the usage of Liquid Organic Hydrogen Carriers (LOHC) for the storage and subsequently the transport of renewable energy. It is expected that a significant share of future energy consumption will be satisfied with the import of energy coming from regions with high potential for renewable generation, e.g. the import of solar power from Northern Africa to Europe. In this context the transport of energy in form of chemical carriers is proposed supplementary to electrical transmission. Because of their high storage density and good manageability under ambient conditions Diesel-like LOHC substances could be transported within the infrastructure that already exists for the handling of liquid fossil fuels (e.g. oil tankers, tank trucks, pipelines, etc.). A detailed assessment of energy consumption as well as of transport costs is conducted that confirms the feasibility of the concept. ► Storage and transport of renewable energy via Liquid Organic Hydrogen Carriers (LOHC). ► LOHC substances could be distributed via the existing infrastructure for liquid fossil fuels. ► Hydrogen transport via LOHC shows very favorable economics. ► Renewable energy imported as hydrogen could be cost-competitive compared to on-site production.

[Display omitted] •Vapor-feed DIFC enabling the direct energy generation out of LOHC-bound hydrogen.•Record-high power densities of a direct isopropanol fuel cell with 254 mW/cm2 at 0.55 V.•High temperature lead to enhanced reaction kinetics and fast desorption of acetone. Liquid Organic Hydrogen Carrier (LOHC) systems offer a very interesting option for hydrogen storage in the existing infrastructure for common fuels. Technically most attractive is the direct use of LOHC-bound hydrogen in a low-temperature PEM fuel cell. Here, the isopropanol/acetone LOHC system is suggested to produce electricity from a condensable liquid without CO2 emissions. A high-performance direct isopropanol fuel cell using a vaporizer and a commercial fuel cell test system is demonstrated. For the first time backpressure is used to enhance the performance. The self-fabricated GDEs combined with a Nafion composite membrane achieved a power density of 203 mW cm−2 for Isopropanol/Air operation at 300 kPa absolute and 85 °C. By increasing the operation temperature to 100 °C a peak power density of 254 mW cm−2 is achieved, exceeding the highest reported values for isopropanol fuel cells operated with air by over 80%. The observed increase in performance can be attributed to the higher reaction rate of the electrooxidation of isopropanol at the anode side during pressurized conditions and to the reduced acetone-poisoning of the Pt-Ru catalyst at elevated temperatures.

Beech lignin was oxidatively cleaved in ionic liquids to give phenols, unsaturated propylaromatics, and aromatic aldehydes. A multiparallel batch reactor system was used to screen different ionic liquids and metal catalysts. Mn(NO3)2 in 1‐ethyl‐3‐methylimidazolium trifluoromethanesulfonate [EMIM][CF3SO3] proved to be the most effective reaction system. A larger scale batch reaction with this system in a 300 mL autoclave (11 g lignin starting material) resulted in a maximum conversion of 66.3 % (24 h at 100 °C, 84×105 Pa air). By adjusting the reaction conditions and catalyst loading, the selectivity of the process could be shifted from syringaldehyde as the predominant product to 2,6‐dimethoxy‐1,4‐benzoquinone (DMBQ). Surprisingly, the latter could be isolated as a pure substance in 11.5 wt % overall yield by a simple extraction/crystallization process. Beech lignin is oxidatively cleaved in ionic liquids to give phenols, unsaturated propylaromatics, and aromatic aldehydes. By adjusting the reaction conditions and catalyst loading, the selectivity of the process can be shifted from syringaldehyde as the predominant product to 2,6‐dimethoxy‐1,4‐benzoquinone (DMBQ).

A new class of biofriendly ionogels produced by gelation of microcellulose thin films with tailored 1‐ethyl‐3‐methylimidazolium methylphosphonate ionic liquids are demonstrated. The cellulose ionogels show promising properties for application in flexible electronics, such as transparency, flexibility, transferability, and high specific capacitances of 5 to 15 μF cm−2. They can be laminated onto any substrate such as multilayer‐coated paper and act as high capacitance dielectrics for inorganic (spray‐coated ZnO and colloidal ZnO nanorods) and organic (poly[3‐hexylthiophene], P3HT) electrolyte‐gated field‐effect transistors (FETs), that operate at very low voltages (

Energy storage via liquid organic hydrogen carrier (LOHC) systems has gained significant attention in recent times. A dibenzyltoluene (DBT) based LOHC offers excellent properties which largely solve today's hydrogen storage challenges. Understanding the course of the dehydrogenation reaction is important for catalyst and process optimization. Therefore, reliable and exact methods to determine the degree of hydrogenation (doh) are important. We here present other possible techniques, namely: comprehensive two-dimensional gas chromatography coupled with time of flight mass spectrometry (2D-GC-TOF-MS) and single quadrupole-mass spectrometry gas chromatogram system (GC-SQ-MS). The 2D-GC-TOF-MS results indicate that isomer fractions lose three molecules of hydrogen, as follows: H18-DBT, H12-DBT, H6-DBT and H0-DBT, and the doh decreases with an increase in dehydrogenation temperature. 1H NMR and GC-SQ-MS were employed as additional analytical techniques. The GC-SQ-MS was also used to analyse decomposition products that result from thermal cracking of reaction mixture molecules. [Display omitted] •Regular GC is not sufficient for analysis of isomeric mixtures of dibenzyltoluene.•Complex mixtures can be separated by 2D-GC-TOF-MS with suitable columns.•Identification of DBT isomer fraction ions by using the SIM of GC-SQ-MS.•High and low boilers decomposition products are detected using GC-SQ-MS.•Higher temperatures (>290 °C) may reduce the life cycle of dibenzyltoluene.

This work contributes to the characterization of the liquid organic hydrogen carrier (LOHC) system diphenylmethane/dicyclohexylmethane by the experimental determination and molecular simulation of the thermophysical properties of the dehydrogenated and fully hydrogenated compounds in a process-relevant temperature range of up to 623 K. Liquid density, liquid viscosity, surface tension and liquid self-diffusion coefficient data measured by vibrating-tube densimeters, surface light scattering, rotational viscometry and NMR spectroscopy are correlated and compared with available literature data which are mostly restricted to temperatures below 473 K. Furthermore, it is demonstrated that an L-OPLS force field (FF) modified in the present study outperforms commonly used FFs from literature in predicting the thermophysical properties of both substances by equilibrium molecular dynamics simulations. [Display omitted] •A new force field for the LOHC system DPM/DCM was developed and validated.•Thermophysical properties of DPM and DCM were measured and simulated up to 623 K.•DPM shows a higher surface tension, density and self-diffusion coefficient.•DCM shows a higher dynamic viscosity especially at low temperatures.•At high temperature, the viscosities of DPM and DCM converge.

Applications of ionic liquids to replace conventional solvents in homogeneous transition‐metal catalysis have increased significantly during the last decade. Biphasic ionic liquid/organic liquid systems offer advantages with regard to product separation, catalyst stability, and recycling but utilise in the case of fast chemical reactions only a small amount of expensive ionic liquid and catalyst. The novel Supported Ionic Liquid Phase (SILP) catalysis concept overcomes these drawbacks and allows the use of fixed‐bed reactors for continuous reactions. In this Microreview the SILP catalysis concept is surveyed by presenting results for the continuous gas‐phase hydroformylation of propene, as a reaction example. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Ten [C8C1Im]+ (1‐methyl‐3‐octylimidazolium)‐based ionic liquids with anions Cl−, Br−, I−, [NO3]−, [BF4]−, [TfO]−, [PF6]−, [Tf2N]−, [Pf2N]−, and [FAP]− (TfO=trifluoromethylsulfonate, Tf2N=bis(trifluoromethylsulfonyl)imide, Pf2N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C8C1C1Im]+ (1,2‐dimethyl‐3‐octylimidazolium)‐based ionic liquids with anions Br− and [Tf2N]− were investigated by using X‐ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While 1H NMR spectroscopy is found to probe very specifically the strongest hydrogen‐bond interaction between the hydrogen attached to the C2 position and the anion, a comparative XPS study provides first direct experimental evidence for cation–anion charge‐transfer phenomena in ionic liquids as a function of the ionic liquid’s anion. These charge‐transfer effects are found to be surprisingly similar for [C8C1Im]+ and [C8C1C1Im]+ salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions. Charges in charged systems: Anion and cation interactions in ionic liquids strongly modify the charges on the ions as proven by XPS, NMR spectroscopy and DFT calculations. The smaller, more basic and, thus, more strongly coordinating the anion, the more pronounced the charge transfer to the cation (see graphic). Hydrogen‐bonding‐type interactions between anion and cation do not significantly influence the amount of charge transferred.

A novel gas‐phase process has been developed that allows direct two‐step conversion of butane into pentanals with high activity and selectivity. The process consists of alkane dehydrogenation over a heterogeneous Cr/Al2O3 catalyst followed by direct gas‐phase hydroformylation using advanced supported ionic liquid phase (SILP) catalysis. The latter step uses rhodium complexes modified with the diphosphite ligands biphephos (BP) and benzopinacol to convert the butane/butene mixture from the dehydrogenation step efficiently into aldehydes. The use of the BP ligand results in improved yields of linear pentanal because SILP systems with this ligand are active for both isomerization and hydroformylation. © 2014 American Institute of Chemical Engineers AIChE J, 61: 893–897, 2015

One of the greatest challenges to science in the 21 st century is the development of efficient energy production, storage, and transformation systems with minimal ecological footprints. Due to the lack of efficient heat‐transformation technologies, industries around the world currently waste energy in the gigawatt range at low temperatures (40–80 °C). These energy potentials can be unlocked or used more efficiently through a new generation of smart heat pumps operating with novel ionic liquid (IL)‐based working pairs. The new technology is expected to allow revolutionary technical progress in heat‐transformation devices, for example, significantly higher potential efficiencies, lower specific investments, and broader possibilities to incorporate waste energy from renewable sources. Furthermore, due to drastically reduced corrosion rates and excellent thermal stabilities of the new, IL‐based working pairs, the high driving temperatures necessary for multi‐effect cycles such as double‐ or triple‐effect absorption chillers, can also be realized. The details of this novel and innovative heat‐transformation technology are described. Pump & Circumstance: The enormous energetic potential of low‐caloric heat streams (40–80 °C) can be unlocked through a new generation of smart heat pumps operating with novel ionic liquid (IL)‐based working pairs. The new technology is expected to allow significantly higher potential efficiencies, lower specific investments and broader possibilities to incorporate heat from renewable sources.

The advantages of heterogeneous catalysis and transition‐metal catalysis in ionic liquids are combined in rhodium bisphosphine catalysts in an ionic‐liquid phase on a silica support. These active, regioselective, and highly stable catalysts were applied in a fixed‐bed reactor for the continuous‐flow gas‐phase hydroformylation of propene.

The cat. that got the butene: Highly active and selective diphosphite ligands are applied for rhodium‐catalyzed supported ionic liquid phase (SILP) hydroformylation and make it possible to form linear n‐pentanal with exceptional selectivity from a mixed butene feedstock by combined isomerization and hydroformylation (see picture, vials 1–4 show typical SILP catalysts employed in this study.). The SILP catalyst is stable for more than 800 h on stream.

Mixing ionic liquids is a suitable strategy to tailor properties, e.g., to reduce melting points. The present study aims to widen the application range of low-toxic choline-based ionic liquids by studying eight binary phase diagrams of six different choline carboxylates. Five of them show eutectic points with melting points dropping by 13 to 45 °C. The eutectic mixtures of choline acetate and choline 2-methylbutarate were found to melt at 45 °C, which represents a remarkable melting point depression compared to the pure compounds with melting points of 81 (choline acetate) and 90 °C (choline 2-methylbutarate), respectively. Besides melting points, the thermal stabilities of the choline salt mixtures were investigated to define the thermal operation range for potential practical applications of these mixtures. Typical decomposition temperatures were found between 165 and 207 °C, with choline lactate exhibiting the highest thermal stability.

Dodecahydro‐N‐ethylcarbazole (H12‐NEC) has been proposed as a potential liquid organic hydrogen carrier (LOHC) for chemical energy storage, as it combines both favourable physicochemical and thermodynamic properties. The design of optimised dehydrogenation catalysts for LOHC technology requires a detailed understanding of the reaction pathways and the microkinetics. Here, we investigate the dehydrogenation mechanism of H12‐NEC on Pd(111) by using a surface‐science approach under ultrahigh vacuum conditions. By combining infrared reflection–absorption spectroscopy, density functional theory calculations and X‐ray photoelectron spectroscopy, surface intermediates and their stability are identified. We show that H12‐NEC adsorbs molecularly up to 173 K. Above this temperature (223 K), activation of CH bonds is observed within the five‐membered ring. Rapid dehydrogenation occurs to octahydro‐N‐ethylcarbazole (H8‐NEC), which is identified as a stable surface intermediate at 223 K. Above 273 K, further dehydrogenation of H8‐NEC proceeds within the six‐membered rings. Starting from clean Pd(111), CN bond scission, an undesired side reaction, is observed above 350 K. By complementing surface spectroscopy, we present a temperature‐programmed molecular beam experiment, which permits direct observation of dehydrogenation products in the gas phase during continuous dosing of the LOHC. We identify H8‐NEC as the main product desorbing from Pd(111). The onset temperature for H8‐NEC desorption is 330 K, the maximum reaction rate is reached around 550 K. The fact that preferential desorption of H8‐NEC is observed even above the temperature threshold for H8‐NEC dehydrogenation on the clean surface is attributed to the presence of surface dehydrogenation and decomposition products during continuous reactant exposure. Renewable hydrogen fuel: Over a Pd(111) surface, dodecahydro‐N‐ethylcarbazole, a liquid organic hydrogen carrier, adsorbs at temperatures up to 173 K. At temperatures close to 223 K, CH bonds in the 5‐membered ring are activated and, at 273 K, those of the 6‐membered ring are activated. Undesired side reactions, such as CN cleavage, occur above 273 K (see scheme).

⿢We examine the regeneration of Pt-based catalysts poisoned by LOHC degradation.⿢A microscopic mechanism of the removal of degradation products from Pt is proposed.⿢Results of our UHV studies on model catalysts are transferred to real catalysis.⿢Oxidative regeneration of Pt/alumina is possible under mild conditions (600K).⿢The degree and temperature regime of regeneration depends on the catalyst morphology. The Liquid Organic Hydrogen Carrier (LOHC) concept offers an efficient route to store hydrogen using organic compounds that are reversibly hydrogenated and dehydrogenated. One important challenge towards application of the LOHC technology at a larger scale is to minimize degradation of Pt-based dehydrogenation catalysts during long-term operation. Herein, we investigate the regeneration of Pt/alumina catalysts poisoned by LOHC degradation. We combine ultrahigh vacuum (UHV) studies on Pt(111), investigations on well-defined Pt/Al2O3 model catalysts, and near-ambient pressure (NAP) measurements on real core⿿shell Pt/Al2O3 catalyst pellets. The catalysts were purposely poisoned by reaction with the LOHC perhydro-dibenzyltoluene (H18-MSH) and with dicyclohexylmethane (DCHM) as a simpler model compound. We focus on oxidative regeneration under conditions that may be applied in real dehydrogenation reactors. The degree of poisoning and regeneration under oxidative reaction conditions was quantified using CO as a probe molecule and measured by infrared reflection-absorption spectroscopy (IRAS) and diffuse reflectance Fourier transform IR spectroscopy (DRIFTS) for planar model systems and real catalysts, respectively. We find that regeneration strongly depends on the composition of the catalyst surface. While the clean surface of a poisoned Pt(111) single crystal is fully restored upon thermal treatment in oxygen up to 700K, contaminated Pt/Al2O3 model catalyst and core⿿shell pellet were only partially restored under the applied reaction conditions. Whereas partial regeneration on facet-like sites on supported catalysts is more facile than on Pt(111), carbonaceous deposits adsorbed at low-coordinated defect sites impede full regeneration of the Pt/Al2O3 catalysts.

This study explores the tuning of a Pd/Al2O3 hydrogenation catalyst for the selective removal of trace acetylene from ethylene-rich feeds by coating the catalyst with non-functionalized and functionalized ionic liquids (denoted as SCILL and Advanced SCILL materials, respectively). These materials were tested in an automated continuous hydrogenation rig converting 3300 ppm of acetylene in excess ethylene, a gas mixture mimicking a technical front-end steam cracker feed composition. While the sulfonic-acid-functionalized IL coating resulted in a highly active but very unselective catalyst converting mainly ethylene to ethane, an Advanced SCILL catalyst prepared from a nitrile-functionalized IL reduced the acetylene concentration down to less than 1 ppm, while leaving over 99% of the ethylene untouched. We also examined the potential transformations of the IL layer under reaction conditions by means of 1H NMR. Except for a ketone-functionalized IL, which was inherently labile, all tested ILs primarily underwent C2-ethylation or remained unaltered. Our findings highlight the great potential of functionalized ILs in modifying heterogeneous hydrogenation catalysts. [Display omitted]

Liquid organic hydrogen carriers can store hydrogen in a safe and dense form through covalent bonds. Hydrogen uptake and release are realized by catalytic hydrogenation and dehydrogenation, respectively. Indoles have been demonstrated to be interesting candidates for this task. The enthalpy of reaction is a crucial parameter in this regard as it determines not only the heat demand for hydrogen release, but also the reaction equilibrium at given conditions. In this work, a combination of experimental measurements, quantum chemical methods and a group-additivity approach has been applied to obtain a consistent dataset on the enthalpies of formation of different methylated indole derivatives and their hydrogenated counterparts. The results show a namable influence of the number and position of methyl groups on the enthalpy of reaction. The enthalpy of reaction of the overall hydrogenation reaction varies in the range of up to 18.2 kJ·mol (corresponding to 4.6 kJ·mol(H ) ). The widest range of enthalpy of reaction data for different methyl indoles has been observed for the last step (hydrogenation for the last double bond in the five-membered ring). Here a difference of up to 7.3 kJ·mol(H ) between the highest and the lowest value was found.

Isolated active sites have great potential to be highly efficient and stable in heterogeneous catalysis, while enabling low costs due to the low transition metal content. Herein, we present results on the synthesis, first catalytic trials, and characterization of the Ga Rh phase and the hitherto not-studied Ga Rh phase. We used XRD and TEM for structural characterization, and with XPS, EDX we accessed the chemical composition and electronic structure of the intermetallic compounds. In combination with catalytic tests of these phases in the challenging propane dehydrogenation and by DFT calculations, we obtain a comprehensive picture of these novel catalyst materials. Their specific crystallographic structure leads to isolated Rhodium sites, which is proposed to be the decisive factor for the catalytic properties of the systems.

Alkyl-cyclohexanes can be considered as suitable model compounds to understand the thermochemistry of aromatic compounds and their hydrogenated counterparts discussed as Liquid Organic Hydrogen Carrier systems. Thermochemical measurements on these hydrogen-rich compounds are thwarted by complications due to the 99.9 % purity limitation and sample size specific to these methods. However, the data on vaporisation and formation enthalpies are necessary to optimize the hydrogenation/dehydrogenation processes. In this work, various empirical and theoretical methods are described to reliably assess the gas phase enthalpies of formation and vaporization enthalpies of alkyl-substituted cyclohexanes. The empirical and quantum-chemical methods have been validated against reliable literature data and provide reasonable estimates with an accuracy comparable to that of the experimental data. The liquid phase enthalpies of formation of differently shaped alkyl-cyclohexanes were derived and used to estimate the energetics of their dehydrogenation reactions. The influence of alkyl substituents on the reaction enthalpy is discussed. The vapour pressures of typical hydrogen-rich compounds at technically relevant temperatures were calculated and compared to vapour pressures of biodiesel fuels measured in this work using the static method.